content: /**
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  package io.reactivex.observable.internal.observers;
  
  import java.util.concurrent.CountDownLatch;
  
  import io.reactivex.common.Disposable;
  import io.reactivex.common.internal.utils.*;
  import io.reactivex.observable.Observer;
  
  public abstract class BlockingBaseObserver<T> extends CountDownLatch
  implements Observer<T>, Disposable {
  
      T value;
      Throwable error;
  
      Disposable d;
  
      volatile boolean cancelled;
  
      public BlockingBaseObserver() {
          super(1);
      }
  
      @Override
      public final void onSubscribe(Disposable d) {
          this.d = d;
          if (cancelled) {
              d.dispose();
          }
      }
  
      @Override
      public final void onComplete() {
          countDown();
      }
  
      @Override
      public final void dispose() {
          cancelled = true;
          Disposable d = this.d;
          if (d != null) {
              d.dispose();
          }
      }
  
      @Override
      public final boolean isDisposed() {
          return cancelled;
      }
  
      /**
       * Block until the first value arrives and return it, otherwise
       * return null for an empty source and rethrow any exception.
       * @return the first value or null if the source is empty
       */
      public final T blockingGet() {
          if (getCount() != 0) {
              try {
                  BlockingHelper.verifyNonBlocking();
                  await();
              } catch (InterruptedException ex) {
                  dispose();
                  throw ExceptionHelper.wrapOrThrow(ex);
              }
          }
  
          Throwable e = error;
          if (e != null) {
              throw ExceptionHelper.wrapOrThrow(e);
          }
          return value;
      }
  }
  